Self-locking bolt



April 1946.

Q E- G. LER ET AL SELF-LOCKIN BOLT Q Filed April 1944 E. o J W Patented Apr. 23, 1946 SELF-LOCKING BOLT Edward G. Miller and Ralph E. Engberg, New York. N. Y., assignors, by mesne assignments, to Allied Control Company, Inc., New York, N. Y., a corporation of New York Application April 1, 1944, Serial No. 529,070

1 Claim.

This invention relates to self-locking bolts.

An object of this invention is a bolt having provision whereby upon being threaded into a supporting member, it is automatically locked therein against accidental removal.

Onetype of self-locking bolt embodying the invention consists of a shank and a head with the shank being threaded over a portion of its length but having a portion beginning at the head of less cross-section than the threaded portion. The head of the bolt facing the threaded portion is slightly recessed so that the portion of reduced cross-section extends'a short distance into the bolt head. Around the portion of reduced cross-section is arranged an inset of elastic material'having a circular surface of larger diameter than the minor diameter 01- the bolt thread but of no greater diameter than the major diameter of the thread. The configuration of the reduced cross-section portion and the aperture in the inset is such that rotation of the inset relative to the bolt is prevented.

In use, the bolt is screwed into a member having a tapped aperture of greater length than the length of the elastic inset, the threads of which aperture match the threads of the bolt. When the inset enters the tapped aperture, the aperture thread cuts a thread in the-outer surface of the inset and also pushes part of the inset into the bolt head recess. The friction developed between the threads oi the bolt and the member in which it is inserted by reason of the action just above mentioned, results in tightly locking the bolt in the member.

Other objects, novel features and advantages of this invention will become apparent from the following specification and accompanying draw ing, wherein:

Fig. 1 is a side elevation of a bolt embodying o portion of the inset ll. As explained in connection with Fla. 2, a portion of the inset is causedv the invention:

Fig. 2 isa longitudinal section through the bolt illustrating one form of use, and a Fig. 3 is a view similar to Fig. 2 showing another use.

The bolt consists of a head I. which may either be cylindrical and have a screw-driver slot in one face or may be of polygonal cross-section. A shank ll extends from the remaining face of the head and has a portion I! of reduced cross section adjacent said face of the head It. the portion l2 preferably being of polygonal configuration. The remainder of the shank I I beyond the portion is is provided with standard screw threads II. A recess I3 is provided in the face of the head Ill An inset I 5 of elastic material surrounds the portion 12 and has a polygonal aperture conforming to the configuration of said portion. The inset [5 may be a split ring which may be expanded sufliciently to put it in place around the portion l2 or it may be a member molded on the portion l2. The exterior surface of the inset i5 is circular and is of larger diameter than the minor diameter of the threads II but of no greater diameter than the major diameter of said threads. The overall diameter of the inset it slightly exceeds the maximum diameter of the recess It so that normally no portion of the inset It extends into the recess ll.

Fi 2 illustrates one manner of use of the bolt. In this figure. I6 is a metallic member of greater thickness than the length of the inset l5 and has a tapped aperture ll, the threads of which match the threads l4. Introduction of the inset it into the tapped aperture by threading the bolt thereinto causes the threads II to cut corresponding threads in the surface of the inset and also to project part of-the inset I 5 into the recess l3, relative rotation of the inset and bolt being prevented by reason of the matching'polygonal configuration of the portion l2 and the aperture through the inset. The friction-developed between the threads I I and I1 and the friction developed between the end of the inset l5 and the surface of the recess It results in tightly locking the bolt in the member It.

In Fig. 3, I 8 is a metallic member having a tapped aperture and I8 is a metallic member having a smooth surface aperture I9. The bolt shank extends first through the aperture l9 and is threaded into the tapped aperture ii. The inset II is of greater extent than the thickness of the plate I 8 so that threading of the bolt shank It into the tapped aperture i1 cuts threads in a to project into the recess I! to assist in the locking action. 7

We claim:

A self-locking bolt comprising a head having a shank extending from one face thereof, said shank having a portion of reduced polygonal cross-section adjacent said head and having its from which the shank It extends and is of less remainingportion provided with a screw thread.

an elastic inset having a polygonal aperture fltting said portion, said inset being cylindrical and of greater diameter than the minor diameter of said screw thread, and a socket in the face of said head adjacent said inset. EDWARD G. MIILER. RALPH E. ENGBERG. 

